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loading web fonts synchronously during automation
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Bobby Holley
Nov 4, 2015, 10:17:18 PM11/4/15
to mozilla-...@lists.mozilla.org
Right now, every wpt test includes a stylesheet with an @font-face rule to
make the 'ahem' font available to tests. Since font loading triggers a
document-wide reflow, we end up with a non-deterministic network-driven
reflow in each and every test, which makes it harder to test layout
optimizations and increases the chances for intermittent bugs.
In [1] I'm planning to add a debug flag to load web fonts synchronously,
and set that flag in the wpt runner. Please let me know if anyone has any
objections.
Cheers,
bholley
[1] https://github.com/servo/servo/pull/8341
make the 'ahem' font available to tests. Since font loading triggers a
document-wide reflow, we end up with a non-deterministic network-driven
reflow in each and every test, which makes it harder to test layout
optimizations and increases the chances for intermittent bugs.
In [1] I'm planning to add a debug flag to load web fonts synchronously,
and set that flag in the wpt runner. Please let me know if anyone has any
objections.
Cheers,
bholley
[1] https://github.com/servo/servo/pull/8341
L. David Baron
Nov 4, 2015, 10:28:55 PM11/4/15
to Bobby Holley, mozilla-...@lists.mozilla.org
On Wednesday 2015-11-04 19:16 -0800, Bobby Holley wrote:
> Right now, every wpt test includes a stylesheet with an @font-face rule to
> make the 'ahem' font available to tests. Since font loading triggers a
> document-wide reflow, we end up with a non-deterministic network-driven
> reflow in each and every test, which makes it harder to test layout
> optimizations and increases the chances for intermittent bugs.
>
> In [1] I'm planning to add a debug flag to load web fonts synchronously,
> and set that flag in the wpt runner. Please let me know if anyone has any
> objections.
The font shouldn't even load unless it's needed (i.e., there's text
> Right now, every wpt test includes a stylesheet with an @font-face rule to
> make the 'ahem' font available to tests. Since font loading triggers a
> document-wide reflow, we end up with a non-deterministic network-driven
> reflow in each and every test, which makes it harder to test layout
> optimizations and increases the chances for intermittent bugs.
>
> In [1] I'm planning to add a debug flag to load web fonts synchronously,
> and set that flag in the wpt runner. Please let me know if anyone has any
> objections.
that uses it). I *think* that's the way things work across
browsers, and allows inclusion of style sheets that provide a
"library" of @font-face rules that may or may not be used. That
would avoid the reflow except where Ahem is actually used, which
seems like the way things ought to work.
-David
--
𝄞 L. David Baron http://dbaron.org/ 𝄂
𝄢 Mozilla https://www.mozilla.org/ 𝄂
Before I built a wall I'd ask to know
What I was walling in or walling out,
And to whom I was like to give offense.
- Robert Frost, Mending Wall (1914)
Bobby Holley
Nov 4, 2015, 11:15:19 PM11/4/15
to L. David Baron, mozilla-...@lists.mozilla.org
That's a great point - I'll take a look to see how doable it is.
Bobby Holley
Nov 4, 2015, 11:28:46 PM11/4/15
to L. David Baron, mozilla-...@lists.mozilla.org
Seems generally doable, but probably more than I want to chew right now.
I'll get an issue filed though.
Does anyone object to landing the synchronous font loading as a stopgap to
get better reftest coverage until we make the font loading logic smarter?
I'll get an issue filed though.
Does anyone object to landing the synchronous font loading as a stopgap to
get better reftest coverage until we make the font loading logic smarter?
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